We will be using the anti-MuLV antibody already prepared in a complement-dependent mediated technique to isolate ts mutants. Clones will also be picked from mutagenized stocks. The defect of ts3, which seems to be in the glycoprotein will be further characterized using autoradiography and gel electrophoresis with C14-labelled amino-acid viral proteins and glucosamine-H3 glycoproteins. If the glycoprotein of ts3 is defective we would like to find out how it differs from that of the wt and how an altered glycoprotein affects dissociation of the virions from the cell membrane. The relationship between enveloped A and type C particles has never been fully investigated. Since the dissociation of ts3 virions from the cell membranes can be switched on and off by altering the temperature, we hope to investigate the steps in the assembly of the virions and the structural changes that occur in the maturing virion using the transmission electron microscope. We will also investigate the defective functions of other ts mutants we isolated, i.e. ts1, ts2, and ts7. BIBLIOGRAPHIC REFERENCES: Wong, P.K.Y. and Macleod, R. (1975). Studies on the budding process of a temperature sensitive mutant of murine leukemia virus with a scanning electron microscope. J. of Virology 16, 434-442.